Monitoring and Assessment Links

2012 Activity Report Field Surveys

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Oyster Sanctuaries

April-May

Initiated a monitoring program for the recently established tributary-scale oyster sanctuaries in Maryland. A patent-tong based survey framework was developed and implemented in seven sanctuaries throughout the state in collaboration with the MDNR Shellfish Restoration Program. The surveys provided baseline data to evaluate the efficacy of the sanctuary initiative. Approximately 1200 samples were taken, each with data collected on oyster abundance, size frequency, observed mortality, recent recruitment, and habitat information including substrate type and estimates of shell volume per unit area.

Coastal Bays Shellfish Assessment

June

Completed the 18th annual Coastal Bays Shellfish Survey. The survey has been tracking how hard clam populations have responded to the ban on mechanical harvesting in 2008 and consequent decrease in fishing pressure. A total of 260 samples were taken at random, stratified by bay or bay quadrant using the commercial clam dredger Sea Whore equipped with a hydraulic escalator dredge. Currently, hard clam populations are either stable or have increased throughout the bays. Isle of Wight Bay had the highest densities, with an overall mean approaching historic levels. However, recruitment appeared to be low. The most encouraging news was the second year of improved densities in Chincoteague Bay after a long period of decline to alarmingly low levels. Although spotty, recruitment appeared to be the best among the bays, resulting in a doubling in density over the past two years. Nevertheless, the average density for Chincoteague Bay remains much lower than the historic baseline.

Although hard clams are the primary focus of this survey, other commercially and ecologically valuable molluscan species are accounted for as well. Of particular interest is the status of the bay scallop population, which was re-introduced to the Coastal Bays by the MDNR Shellfish Program during the late 1990's.Unfortunately, this population is struggling - only one bay scallop was found (in Isle of Wight Bay); none were observed last year. Also surveyed was the only known subtidal oyster population in Chincoteague Bay, where oysters approached 6 inches in length and there continued to be spat set, albeit light. A sample of oysters was taken to the Cooperative Oxford Lab for disease analyses.

August

Initiated an experiment to test oyster disease virulence or tolerance of oysters from Chincoteague Bay. Disease results from the June survey were negative for the subtidal oyster population in Chincoteague Bay. To test whether these oysters are resistant to disease or if disease is absent, a sample was collected and transferred to Deal Island where disease is known to be enzootic. Disease levels in these oysters will be compared with a local population of Tangier Sound oysters after a year of exposure. The Oxford Lab has agreed to analyze the oysters for diseases.

Razor Clam Mortalities

July

Acting on reports from commercial clammers of abnormally high razor clam mortalities, five locations in the Patuxent River were sampled using a hydraulic escalator dredge. In addition to population assessments, specimens were sent to the Cooperative Oxford Lab for disease analysis and water samples were collected for evidence of harmful algal blooms. The latter was part of a collaborative effort with the MDNR Resource Assessment Service. Razor clam observed mortalities ranged from 26% up to 82%. Although there was no clear-cut "smoking gun", disseminated neoplasia, a blood disease fatal to soft clams and believed responsible for large-scale mortalities in razor clams, was found in 43% and 47% of the razor clams from two samples. Also noteworthy was that no softshell clams were observed, although several areas were surveyed where that species had been collected in past years.

Potomac River Fisheries Commission Oyster Reserve

June/October

The PRFC established a pilot program for a self-sustaining oyster fishery which could serve as a prototype for future oyster management in the Bay. In support of the program, MDNR surveyed and delineated a seed planting area on Ragged Point bar. Afterwards, the area was planted with triploid oysters from the Piney Point hatchery. The planting was examined in October and appeared to be doing extremely well. The four-month old oysters averaged an impressive 51 mm in shell height. Overall mortality from the time of planting to the survey date was about 35%.

St. Mary's River Aquaculture Leases

September

Due to the controversy of shellfish aquaculture leasing within the St. Mary's River Oyster Sanctuary, an intensive patent-tong survey of the proposed lease sites was conducted to determine densities and distributions of existing oyster populations on these sites. Eleven proposed leases varying in size from 0.6 acres to 33.6 acres were examined and the findings were provided to the MDNR Aquaculture Division for a management determination. A total of 131 samples were taken, each with data collected on oyster abundance, size frequency, observed mortality, recent recruitment, and habitat information including substrate type and estimates of shell volume per unit area.

Annual Fall Oyster Survey

October-December

The 2012 Fall Oyster Survey, a two-month endeavor which encompassed 262 oyster bars and 316 samples throughout the bay and its tributaries, concluded on 3 December. Preliminary results indicate that oyster populations continue to thrive in most parts of Maryland's Chesapeake Bay, thanks to persistently high survivorship of the strong 2010 year class. Hurricane Sandy appears to have had little effect on the oyster populations, as opposed to 2011 when high freshwater flows from heavy rains in the spring and two tropical storms in late summer impacted oysters in the Upper Bay. As a result, the 2012 Oyster Biomass Index, a measure of oyster abundance and weight, increased for the second consecutive year and is at its highest point since 1999. Spatset also improved dramatically over 2011, marking the second year of above average recruitment in the past three years. Overall total observed mortality was at an all-time low within the 28-year Mortality Index set. Although oyster diseases remained below the long-term average, dermo disease prevalence and mean intensity rose substantially over the record-low 2011 values.

Power Dredge Evaluation

November-December

Completed the second year of a five–year evaluation of the effects of power dredging on oyster populations and habitat. A total of 620 patent tong samples were taken from four specially designated power dredge areas located in three salinity regimes, along with three proximate control sites where power dredging was prohibited. Data were collected on oyster abundance, size frequency, observed mortality, recent recruitment, and habitat information including substrate type and estimates of shell volume per unit area.

Oyster Shell Reclamation Evaluations

December

Conducted a shell reclamation evaluation utilizing patent tongs on Mountain Point and Six Foot Knoll shell borrow sites in the Upper Bay and a dredge on three Back Cove shell planting locations in Tangier Sound. Unfortunately, the borrow site on Mountain Point was on the Fall Oyster Survey Key Bar spatfall monitoring station, which consequently had to be moved to a less suitable location. Of the three Back Cove planting sites, two had little if any shell and the third had undesirable numbers of small and market oysters mixed in. Also, the spat count was relatively low for a seed production planting, with the best site averaging about 250 spat/bu.

Oyster Biomass Index

As part of the governor's "Managing for Results" initiative, calculated the 2011 oyster Biomass Index based on the 2011 Fall Oyster Survey results, and reviewed/updated/ edited the associated document. Implemented shipboard quality assurance procedures for data recording.